In which cases is adding an index not always a successful solution?

Adding an index to a database does not always improve performance. Here are situations where it might be an unsuccessful decision:

• If the table is small, an index may only add overhead to data updates.
• During frequent insert, update, or delete operations, indexes slow down these operations because they need to maintain the index structure.
• If queries do not use the fields on which the index is created, it will not be effective.
• Creating too many indexes increases the load on storage and maintenance.

Therefore, it is important to analyze the nature of queries and the load on the database before adding an index.